What type of research method is good at generating data about an entire population? sociology?

You are a newspaper publisher. you are in the middle of a one-year rental contract for your factory that requires you to pay $500,000 per month, and you have contractual labor obligations of $1 million per month that you can't get out of. you also have a marginal printing cost of $.25 per paper as well as a marginal delivery cost of $.10 per paper. if sales fall by 20 percent from 1 million papers per month to 800,000 papers per month, what happens to the afc per paper?